Recently, attention has been increasingly focused on light emitting devices using LEDs or LDs, as next-generation light emitting devices to replace fluorescence lamps and incandescent lamps, from the viewpoint of their low power consumption, small size, light weight, and easy adjustment to light intensity. For example, Patent Literature 1 discloses, as an example of such a next-generation light emitting device, a light emitting device in which a wavelength conversion member is disposed on an LED for emitting a blue light and absorbs part of the light from the LED to convert it to a yellow light. This light emitting device emits a white light which is a synthetic light of the blue light emitted from the LED and the yellow light emitted from the wavelength conversion member.
As a wavelength conversion member, there is conventionally used a wavelength conversion member in which inorganic phosphor powder is dispersed in a resin matrix. However, when such a wavelength conversion member is used, there arises a problem that the resin is deteriorated by light from the LED to make it likely that the luminance of the light emitting device will be low. Particularly, the wavelength conversion member has a problem in that the molded resin is deteriorated by heat and high-energy short-wavelength (blue to ultraviolet) light emitted from the LED to cause discoloration or deformation.
To cope with the above, a wavelength conversion member is proposed which is formed of an absolutely inorganic solid in which a phosphor is dispersed and set in, instead of resin, a glass matrix (see, for example, Patent Literatures 2 and 3). This wavelength conversion member has the feature that glass as the matrix is less likely to be deteriorated by heat and irradiation light from the LED and therefore less likely to cause problems of discoloration and deformation.